Are you and I going to have a spat on this? I’ll go home and see what sources I have regarding specific troop transfers, but my recollection is that most of the troops were already there, but heavily augmented. The biggest delay was shipping supplies, munitions and trucks to the east in anticipation of the offensive.
I’ll see what my sources say, though.
I agree Stalin had troops in the Far East to guard against any Japanese attack, but until 1944 and the success of Operation Bagration he really couldn't afford to fight Japan at the same time as Germany. Even after that he wanted to concentrate on Europe to grab as much of Germany and Central Europe as he could.